scm: add utc-offset and date-object methods

Add methods for getting the utc-offset of message, and get the sent-date
as an SRFI-19 date object.

scm/mu-scm-test.scm

@@ -1,6 +1,7 @@
 ;; unit tests
 
 (use-modules (mu) (srfi srfi-64)
+             (srfi srfi-19)
 	     (ice-9 textual-ports))
 
 (define (test-store)
@@ -60,10 +61,19 @@
 
 (define (test-mfind)
   (test-begin "test-mfind")
-  (let ((msg (car (mfind "to:a@example.com" #:sort-field 'date #:reverse? #t))))
-    (test-equal "test with multi to and cc" (subject msg) )
+  (let* ((msg (car (mfind "to:a@example.com" #:sort-field 'date #:reverse? #t)))
+         (dateobj (date-object msg)))
+    (test-equal "test with multi to and cc" (subject msg))
     (test-equal "2016-05-15 16:57:25"
-      (time->string (date msg) #:format "%F %T" #:utc? #t)))
+      (time->string (date msg) #:format "%F %T" #:utc? #t))
+    (test-equal -7200 (utc-offset msg))
+    (test-equal 2016 (date-year dateobj))
+    (test-equal 5 (date-month dateobj))
+    (test-equal 15 (date-day dateobj))
+    (test-equal 14 (date-hour dateobj))
+    (test-equal 57 (date-minute dateobj))
+    (test-equal 25 (date-second dateobj))
+    (test-equal 0 (date-nanosecond dateobj)))
   (test-end "test-mfind"))
 
 (define (test-message-full)
@@ -73,13 +83,11 @@
     (test-equal "Motörhead" (header msg "Subject"))
     (test-equal "Mü <testmu@testmu.xx>" (header msg "From"))
     (test-equal #f (header msg "Bla"))
-
     (test-equal (string-append "\nTest for issue #38, where apparently searching for "
 			       "accented words in subject,\nto etc. fails.\n\n"
 			       "What about here? Queensrÿche. Mötley Crüe.\n\n\n")
       (body msg))
     (test-equal #f (body msg #:html? #t))
-
     (test-end "test-message-full")))
 
 (define (test-message-more)
@@ -107,7 +115,6 @@
     (test-equal 'normal (assoc-ref alist 'priority))
     (test-equal '((email . "anon@example.com") (name . "Mickey Mouse"))
       (car  (assoc-ref alist 'from)))
-
     ;; language
     (test-equal (language msg)
       (if (assoc-ref (configuration) 'language-enabled?) 'en #f))

scm/mu-scm.scm

@@ -21,6 +21,7 @@
   :use-module (system foreign)
   :use-module (rnrs bytevectors)
   :use-module (srfi srfi-1) ;; lists
+  :use-module (srfi srfi-19) ;; date/time
   :use-module (ice-9 optargs)
   :use-module (ice-9 format)
   :use-module (ice-9 binary-ports)
@@ -40,6 +41,9 @@
 	    message->alist
 
 	    date
+            date-object
+            utc-offset
+
 	    changed
 
 	    message-id
@@ -214,7 +218,6 @@ CONTENT-ONLY? is implied to be #t."
 Either the 'filename' field in the mime-part and if that does not exist, use
 'mime-part-<index>' with <index> being the number of the mime-part.")
 
-
 (define* (make-output-file mime-part #:key (path #f) (overwrite? #f))
   "Create a port for the file to write MIME-PART to.
 
@@ -331,6 +334,21 @@ path of the message."
 This is the number of seconds since epoch; #f if not found."
   (assoc-ref (message->alist message) 'date))
 
+(define-method (utc-offset (message <message>))
+  "Get the UTC offset in seconds for this MESSAGE.
+I.e., the offset from the UTC for the time the message was sent.
+#f if not available."
+    (assoc-ref (message->alist message) 'utc-offset))
+
+(define-method (date-object (message <message>))
+  "Get an SRFI-19 date object for MESSAGE's sent date.
+This includes the date and the timezone (if known). #f if not found."
+  (let ((unix-time (date message)) (offset (utc-offset message)))
+    (if unix-time
+        (time-utc->date (make-time 'time-utc 0 unix-time)
+                        (or offset 0))
+        #f)))
+
 (define-method (changed (message <message>))
   "Get the timestamp for the last change to MESSAGE.
 This is the number of seconds since epoch; #f if not found."
@@ -661,7 +679,7 @@ If FIELD does not exist, return #f."
   "Alist with user-preferences.
 - short-date: a strftime-compatibie string for the display
 	      format of short dates.
-- utc?       : whether to assume use UTC for dates/times")
+- utc?       : whether to assume UTC for dates/times")
 
 (define (value-or-preference val key)
   "If VAL is the symbol 'preference, return the value for KEY from %preferences.

scm/mu-scm.texi

@@ -613,6 +613,24 @@ For example:
 => 2025-06-16T09:00:31
 @end lisp
 
+@deffn {Scheme Procedure} date-object message
+@end deffn
+Get the message's @t{Date} field (the sent-date) in the form of an SRFI-19
+date-object, or @t{#f} if there is none.
+
+@deffn {Scheme Procedure} utc-offset message
+@end deffn
+Get the message's time-zone offset in seconds; negative for west of GMT,
+positive for east of GMT, or @t{#f} if there is none.
+
+For example:
+@lisp
+(date-object msg)
+=> #<date nanosecond: 0 second: 25 minute: 57 hour: 14 day: 15 month: 5 year: 2016 zone-offset: -7200>
+(utc-offset msg)
+=> -7200
+@end lisp
+
 @deffn {Scheme Procedure} body message  [#:html? #f]
 @end deffn
 Get the message body as a string, or return @code{#f} if not found.